A magnetic proximity switch is a proximity sensor that uses a magnetic element to detect the position variation of nearby objects, and is capable of converting the non-electrical quantities or electromagnetic quantities into required electrical signals, thereby achieving the controlling and measuring purposes. Specifically, in the field of robot application technologies, automatic navigation and positioning detection are crucial for achieving an intelligent control. Compared with commonly-used controllers, proximity switches possess significant advantages in positioning detection and execution control. Due to the high performances of target detection and safety control, magnetic proximity switches are widely applied in various industries such as magnetic-fuse bomb heads, magnetic-detection underwater mines, spacecraft magnetic-flux-gate, high-speed trains, automatic elevators, thermo-magnetic power generation systems, automatic processing equipments, automobile speed control systems, automobile skylight control systems, door switches, cover opening and closing mechanisms and pressure detection devices, etc.
Chinese patent CN201410299835.1 discloses a novel magnetic proximity switch that comprises a shell, a magnet capable of moving upward and downward within the upper portion of the shell, and two wiring terminal pieces that are disposed at the bottom of the shell in parallel, wherein the upper end of one wring terminal piece is provided with an elastic piece, the middle portion of the shell is provided with a swing-able power-assisted rod and a limiting mechanism that interacts with the power-assisted rod, and the elastic piece is provided with an elastic tongue piece that abuts against the power-assisted portion of the power-assisted rod. Although this design can solve problems, such as the metal fatigue of the elastic tongue piece that is caused by a large travel range of the power-assisted rod and the magnet in the motion mechanism, the swing fulcrum of the power-assisted rod, the power-assisted portion and the moment fulcrum of the elastic tongue piece are located on the same horizontal line, and the force arm between the moment fulcrum and the swing fulcrum is long. Thus, a large ratio between the travel range of one end of the power-assisted rod in the limiting mechanism and the swing range of the power-assisted portion is established, resulting in a low moment conversion efficiency of the power-assisted rod and a poor power-assisted travel effect. The magnet moves upward and downward, thereby propelling the power-assisted rod to swing. Thus, the elastic piece is further propelled to move. Due to the friction existing among the magnet, the shell and the power-assisted rod, the magnet powder or the electroplating layer provided on the components can be easily abraded-off, seriously affecting the reliability of the electrical connection between the contacts of the elastic piece and the wiring terminal piece. Furthermore, although the moment conversion of the power-assisted rod ensures a stable control of the switching-on/off of the large current, the arcing problem occurring between the contacts during the variation of the current load cannot be solved. Furthermore, due to the surface oxidation of the contacts and the metal components, the operating stability and the function life of the products can be seriously affected.
In conclusion, the shortcomings of traditional magnetic proximity switches are urgent problems that need to be solved for those skilled in this field.